Wavelength division multiplex transmission system and communication device

ABSTRACT

A wavelength division multiplex transmission system with substantial functions for avoidance of defects is provided. The system comprises an optical transmission device and an optical receiving device. The optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit, and distributes transmission signals to be transmitted among a plurality of wavelength components, converts the signals into WDM signals, and transmits the WDM signals to a WDM transmission network. The optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit, and restores WDM signals from the WDM transmission network into transmission signals. The operating-system optical transmission unit and/or the standby-system optical transmission unit has optical transmission unit internal defect avoidance means which, upon the occurrence of a prescribed number or fewer of wavelength component transmission defects, avoids defects within the optical transmission unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a wavelength division multiplex transmissionsystem and communication device, and in particular, concernsdefect-avoidance processing.

2. Description of Related Art

The current flow of technology for expansion of the capacity of opticalcommunication systems may be broadly divided into time divisionmultiplex (TDM) methods, and wavelength division multiplex (WDM)methods.

Here, in a WDM method, signals are modulated at, for example, 10 Gbpsper channel. In each channel, signals modulated at different wavelengthsare superposed by a four-channel WDM optical coupler (wavelengthdivision multiplexer), and through transmission in a single opticalfiber, transmission at 40 Gbps can be achieved. Compared with TDMmethods, this WDM method has been regarded as superior due to its easeof upgrading, power division costs, ease of maintenance, and serviceflexibility.

In the case of WDM methods, a transmission signal is distributed amongwavelength components for transmission, so that both the opticaltransmission device and the optical receiving device are provided withprocessing units accommodating each of the wavelength components. In theevent that a defect occurs in any of the processing units accommodatinga wavelength component, ordinary transmission will no longer bepossible.

For this reason, it has previously been proposed that a redundantconfiguration of an operating system and standby system be employed,together with an optical transmission device and optical receivingdevice.

However, even if a redundant configuration is adopted, transmission isnot possible when defects occur in both the operating system and thestandby system. In order to avoid this phenomenon, provision of aplurality of standby systems is conceivable. However, in this case theequipment size is increased, so that practical accommodation is notpossible.

In general, when a defect occurs in the operating system, the standbysystem is used in transmission, and while this standby system is beingused, the operating system is restored to the normal state byreplacement of parts or by other means. However, if there is a longlength of time from occurrence of the defect until replacement of partsor similar in the operating system, the possibility of a defectoccurring in the standby system during this interval is increased.Consequently, shortening of the time until part replacement is desired.

SUMMARY OF THE INVENTION

An object of this invention is to provide a wavelength divisionmultiplex transmission system and communication device with substantialfunctions for avoiding defects.

In order to solve these problems, according to a first aspect of theinvention, a wavelength division multiplex transmission system isprovided in which transmission signals to be transmitted are distributedamong a plurality of wavelength components, converted into WDM signalsand sent to the WDM transmission network, and WDM signals from the WOMtransmission network are restored to the above transmission signals.This system comprises an optical transmission device and an opticalreceiving device. This optical transmission device comprises anoperating-system optical transmission unit and a standby-system opticaltransmission unit; the optical receiving device comprises anoperating-system optical receiving unit and a standby-system opticalreceiving unit. The above operating-system optical transmission unitand/or the above standby-system optical transmission unit have opticaltransmission unit internal defect avoidance means which, upon theoccurrence of a prescribed number or fewer of wavelength componenttransmission defects, avoids defects within the optical transmissionunit.

According to a second aspect of this invention, a communication deviceused in a wavelength division multiplex transmission system is provided.This communication device has a defect detection means which detectsdefects in internal constituent members. This communication devicefurther comprises defect occurrence member transmission means; when adefect is detected by the above defect detection means, defectoccurrence member information is sent to an external maintenance membermanagement terminal which performs management of maintenance members,supply processing, or similar.

BRIEF DESCRIPTION OF THE DRAWINGS

The forgoing and other objects, features and advantages of the presentinvention will be better understood from the following description takenin connection with accompanying drawings, in which;

FIG. 1 is a block diagram showing the system configuration of a firstembodiment of the wavelength division multiplex transmission system ofthis invention;

FIG. 2 is a figure explaining exchange processing of nodes in the WDMtransmission network of the first embodiment of the wavelength divisionmultiplex transmission system of this invention;

FIG. 3 is a block diagram showing the detailed configuration of theoptical transmission device of the first embodiment of the wavelengthdivision multiplex transmission system of this invention;

FIG. 4 is a block diagram showing the detailed configuration of anoptical channel card of the first embodiment of this invention;

FIG. 5 is a block diagram showing the detailed configuration of theoptical receiving device of the first embodiment of this invention;

FIG. 6 is a block diagram showing the functional detailed configurationof the network management device of the first embodiment of thisinvention;

FIG. 7 is a flow chart showing the initial route selection operation ofthe first embodiment of this invention;

FIG. 8 is a flow chart showing the signal distribution operation of thefirst embodiment of this invention;

FIG. 9 is a flow chart showing the transmission quality evaluation andcontrol operation of the first embodiment of this invention;

FIG. 10 is a flow chart showing the rerouting operation, upon occurrenceof an optical channel card defect, of the first embodiment of thisinvention;

FIG. 11 is a flow chart showing the rerouting operation, upon occurrenceof a network element defect, of the first embodiment of this invention;

FIG. 12 is a block diagram showing the configuration of principalcomponents of the optical transmission device in a modification of thefirst embodiment of this invention;

FIG. 13 is a block diagram showing the configuration of principalcomponents of the optical transmission device in a modification of thefirst embodiment of this invention;

FIG. 14 is a block diagram showing the configuration of principalcomponents of the optical transmission device in a modification of thefirst embodiment of this invention;

FIG. 15 is a block diagram showing the configuration of principalcomponents of the optical receiving device in a modification of thefirst embodiment of this invention;

FIG. 16 is a block diagram showing the configuration of principalcomponents of the optical receiving device in a modification of thefirst embodiment of this invention;

FIG. 17 is a block diagram showing the configuration of principalcomponents of the optical receiving device in a modification of thefirst embodiment of this invention;

FIG. 18 is a block diagram showing the configuration of principalcomponents of the optical transmission device of a second embodiment ofthe wavelength division multiplex transmission system of this invention;

FIG. 19 is a block diagram showing the configuration of principalcomponents of the optical receiving device of the second embodiment ofthis invention;

FIG. 20 is a flow chart showing the operation, upon occurrence of anoptical channel card defect, of the second embodiment of the invention;

FIG. 21 is a block diagram showing the configuration of principalcomponents of the optical transmission device of a third embodiment ofthe invention;

FIG. 22 is a block diagram showing an example of the detailedconfiguration of an auxiliary optical channel card (variable-wavelengthoptical channel card) of the third embodiment of this invention;

FIG. 23 is a flow chart showing the operation, upon occurrence of anoptical channel card defect, of the third embodiment of this invention;

FIG. 24 is a block diagram showing an example of the detailedconfiguration of the optical channel card of a fourth embodiment of thisinvention;

FIG. 25 is a block diagram showing the configuration of the wavelengthdivision multiplex transmission system of a fifth embodiment of thisinvention;

FIG. 26 is a block diagram showing the system configuration of amodification of the fifth embodiment of this invention; and,

FIG. 27 is a block diagram showing the configuration of the wavelengthdivision multiplex transmission system of a sixth embodiment of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) First Embodiment

With reference to the drawings, a detailed description of a firstembodiment of the wavelength division multiplex transmission systemaccording to the present invention will be herehinafter given.

It is suitable that the configuration of this first embodiment be theconfiguration of the operating system and/or standby system in a systemadopting a redundant configuration, as in the fifth and sixth aspectsdescribed below.

(A-1) Configuration of First Embodiment

Referring to FIG. 1, the wavelength division multiplex transmissionsystem of the first embodiment has a WDM transmission network 1; anoptical transmission device 3 which converts transmission signals(electrical signals) from a transmission terminal 2 into optical signals(WDM signals) and transmits the optical signals over the WDMtransmission network; an optical receiving device 4 which changes WDMsignals received from the WDM transmission network 1 into electricalsignals and applies the electrical signals to the receiving terminal 5;and a network management device 6 which is responsible for managementfunctions for the WDM transmission network 1, optical transmissiondevice 3, optical receiving device 4, and similar.

(A-1-1) WDM transmission network 1

In the WDM transmission network 1, a plurality of nodes N are connectedin, for example, a mesh shape or a matrix shape. Here, the wavelengthcomponents handled by the WDM transmission network 1 are assumed to be aplurality of discrete wavelengths, λ1 to λn, extending from ashort-wavelength end to a long-wavelength end. In this first embodiment,the internal configuration of each node N is omitted from the figure,but a WDM signal input from a given node can be exchanged (or switched)and output for each wavelength component.

FIG. 2 is an explanatory figure illustrating transmission on differentroutes according to the wavelength component.

In the configuration example shown in FIG. 2, when a node N1 is providedwith a WDM signal containing all the wavelength components from λ1 to λnfrom a certain node NS (not shown; this may also be an opticaltransmission device), a WDM signal containing wavelength components λ1and λ2 is applied to node N3, and a WDM signal containing the wavelengthcomponents λ3 to λn is applied to node N4.

When a WDM signal containing wavelength components λ1 and λ2 is appliedto node N3 from node N1, node N3 applies a WDM signal containingwavelength components λ1 and λ2 to node N2. When a WDM signal containingwavelength components λ1 and λ2 is applied to node N3 from a node (notshown) other than node N1, a WDM signal containing wavelength componentsλ1 and/or λ2 can be applied to a node (not shown) other than node N2.Explanation of exchange functions for the other wavelength components λ3to λn of node N3 is omitted.

Similarly, nodes N4 and N5 have, at least, the exchange functions shownin FIG. 2 with respect to WDM signals containing the wavelengthcomponents λ3 to λn.

When a WDN signal containing wavelength components λ1 and λ2 is appliedto node 2 from node N3, node N2 applies to node ND (not shown; may alsobe an optical receiving device) a WDM signal containing wavelengthcomponents λ1 and λ2, and when a WDM signal containing wavelengthcomponents λ3 to λn is applied to node 2 from node N5, node N2 appliesto node ND a WDM signal containing wavelength components λ3 to λn.

That is, FIG. 2 shows an example in which, when sending a WDM signalcontaining all the wavelength components from λ1 to λn from the node NSto the node ND, by means of the route exchange functions (exchangefunctions for each wavelength component) of the WDM transmission network1, the wavelength components λ1 and λ2 are transmitted via the routeRT2, and the wavelength components λ3 to λn are transmitted via theroute RT1.

The above-described exchange processing for each wavelength component ateach node may, for example, rely on labeling information, inserted intothe optical signals for each wavelength component (for example, theheader part), which indicates routes. Or, exchange processing may relyon control signals from the network management device 6.

(A-1-2) Optical transmission device 3

FIG. 3 is a block diagram showing the detailed configuration of theoptical transmission device 3. In FIG. 3, signal lines for electricalsignals are shown as thick lines, and signal lines for optical signalsare shown as thin lines.

In FIG. 3, the optical transmission device 3 has a physical interfaceunit 10, frame termination unit 11, signal distributor 12, opticalchannel cards 13-1 through 13-n, wavelength division multiplexer 15,transmission-side control signal processing unit 17, and othercomponents.

The physical interface unit 10 is responsible for physical interfacefunctions with the transmission terminal 2. The frame termination unit11 performs termination processing for transmission signals(transmission frames) from the transmission terminal 2.

FIG. 3 shows the case in which one transmission terminal 2 is connectedto the optical transmission device 3. When there is a plurality oftransmission terminals 2, a physical interface unit 10 and frametermination unit 11 are provided at each transmission terminal 2.Selection of transmission signals from each transmission terminal 2 maybe performed by providing selection switches, or the signal distributor12 may be endowed with these functions. Here the transmission terminals2 need not be ordinary communication terminals, but may also be routersor similar.

The signal distributor 12 has functions for distributing transmissionsignals from transmission terminals 2 to the optical channel cards 13-1to 13-n, as optical channel units. In the case of a train of packetsignals P1 to Pn, for n transmission signals from a transmissionterminal 2, the signal distributor 12 distributes the packet signal P1to the optical channel card 13-1, the packet signal P2 to the opticalchannel card 13-2, the packet signal P3 to the optical channel card13-3, and so on, until the packet signal Pn is distributed to theoptical channel card 13-n. A plurality of packet signals may also bedistributed to the same channel card. Such a distribution method reliesupon control information from the transmission-side control signalprocessing unit 17.

The signal distributor conforms to, for example, IMP (Inverse MUX forPackets (over SONET/SDH)).

The signal distributor 12 comprises a distribution unit 12 a whichactually executes distribution of signals, and a distribution controlsignal receiving unit (omitted in FIG. 3) which receives distributioncontrol signals from the transmission-side control signal processingunit 17, and applies the signals to the distribution unit 12 a. By thismeans, the signal distributor 12 distributes and applies to the opticalchannel cards 13-1 to 13-n the transmission signals from thetransmission terminals 2, according to distribution control signals fromthe transmission-side control signal processing unit 17.

The first principal function of each of the optical channel cards 13-1,. . . , 13-n is electrical/optical conversion. A different wavelengthλ1, . . . , λn is allocated to each of the optical channel cards 13-1, .. . , 13-n. Each of the optical channel cards 13-1, . . . , 13-nconverts electrical signals (distributed transmission signals) appliedfrom the signal distributor 12 into optical signals for the wavelengthcomponent λ1, . . . , λn allocated to that card, and applies the opticalsignal to the wavelength division multiplexer 15 via the correspondingoptical fiber 14-1, . . . , 14-n.

The wavelength division multiplexer 15 comprises, for example, an n:1optical coupler; it performs wavelength multiplexing of the opticalsignals for each of the arriving wavelength components λ1 to λn, andsends the WDM signals to an optical fiber 16 leading to the WDMtransmission network 1.

As explained above, in the WDM transmission network 1, routes can bechanged according to the wavelength component λ1, . . . , λn.

The second principal function of each of the optical channel cards 13-1,. . . , 13-n is to send evaluation signals to evaluate routes for eachwavelength component in the WDM transmission network 1. Each of theoptical channel cards 13-1, . . . , 13-n sends an evaluation signalunder the control of the transmission-side control signal processingunit 17, notifies the transmission side control signal processing unit17 of the timing with which evaluation signals are sent, and performsother operations. Specifically, each of the optical channel cards 13-1,. . . , 13-n constitutes an optical channel unit.

The transmission-side control signal processing unit 17 is connected tothe network management device 6. This processing unit 17 has functionsfor, for example, specifying the details of distribution by the signaldistributor 12, and controlling the sending of evaluation signals fromeach of the optical channel cards 13-1, . . . , 13-n. While a detaileddiscussion is omitted, the transmission-side control signal processingunit 17 is also responsible for monitoring of each of the opticalchannel cards 13-1, . . . , 13-n, and when a malfunction occurs in anyof the optical channel cards, notifies the network management device 6or similar of this malfunction.

FIG. 4 is a block diagram showing the detailed configuration of theoptical channel cards 13 (13-1, . . . , 13n). In FIG. 4 also, signallines for electrical signals are shown as thick lines, and signal linesfor optical signals are shown as thin lines.

The optical channel cards 13 have an LD (laser diode) light source 20;an optical modulator 21; a modulator driver circuit (in FIG. 4, denotedas a driver circuit) 22; a clock control circuit 23; a signal selectionunit 24; and an evaluation signal generator unit 25.

Here, the LD light source 20, optical modulator 21 and modulator drivercircuit 22 are configured in order to convert ordinary electricalsignals into optical signals. That is, the modulator driver circuit 22drives the optical modulator 21 according to the electrical signal to betransmitted, and based on the clock frequency specified by the clockcontrol circuit 23, to modulate (for example, intensity modulation)optical signals (with the wavelength allocated to the optical channelcard 13) from the LD light source 20, to output modulated opticalsignals. Of course a modulated light source, in which the light sourceis directly controlled for modulation, can also be employed.

In the case of this first embodiment, the optical channel card 13 has aclock control circuit 23, signal selection unit 24, and evaluationsignal generator unit 25.

The evaluation signal generator unit 25 generates an evaluation signal(electrical signal) for evaluation of the route and its transmissioncharacteristics of the wavelength component of the optical channel card13 in the WDM transmission network 1, under the control of the signalselection unit 24. The data pattern of evaluation signals is a patternenabling discrimination from distributed transmission signals. Here thetransmission timing is such that evaluation signals and distributedtransmission signals are temporally differentiated. Further, the opticalchannel cards 31-1, . . . , 13-n shown in FIG. 3, and more specifically,the evaluation signal generator unit 25 shown in FIG. 4 is a constituentcomponent of the transmission characteristic evaluation means.

Distributed transmission signals (electrical signals) are applied fromthe signal distributor 12 to the signal selection unit 24, which at thesame time is connected to the evaluation signal generator unit 25.During intervals in which distributed transmission signals are appliedby the signal distributor 12 according to control signals from thetransmission-side control signal processing unit 17, the signalselection unit 24 selects the distributed transmission signal andapplies it to the modulator driver circuit 22; during intervals in whichdistributed transmission signals are not applied by the signaldistributor 12, the signal selection unit 24 causes the evaluationsignal generator 25 to generate evaluation signals, which are applied tothe modulator driver circuit 22.

That is, whereas distributed transmission signals (optical signals)having the allocated wavelength components are sometimes sent from theoptical channel card 13, evaluation signals (optical signals) having theallocated wavelength components are also sometimes sent.

In the case of this first embodiment, the period of the clock signaloutput by the above-described clock control circuit 23 of the opticalchannel card 13 can be varied by the network management device 6(directly by the control signal processing unit 17). That is,transmission speeds can be switched.

(A-1-3) Optical receiving device 4

FIG. 5 is a block diagram showing the detailed configuration of theoptical receiving device 4. In FIG. 5, signal lines for electricalsignals are shown as thick lines, and signal lines for optical signalsare shown as thin lines.

In FIG. 5, the optical receiving device 4 has a wavelength divisiondemultiplexer 30, optical receiving cards 32-1 to 32-n, delaycompensation unit 33, multiplexer 34, receiving-side control signalprocessing unit 35, and other components.

WDM signals arriving from the WDM transmission network 1 via the opticalfiber 36 are input to the wavelength division demultiplexer 30 of theoptical receiving device 4. The wavelength division demultiplexer 30separates the arriving WDM signal into wavelength components λ1, . . . ,λn, and applies the optical signals of each of the wavelength componentsλ1, . . . , λn to corresponding optical receiving cards 32-1, 32-n, asoptical receiving units, via optical fibers 31-1, 31-n.

The detailed configuration of each of the optical receiving cards 32-1,. . . , 32-n is omitted from thefigure; but after converting the opticalsignals of the wavelength components λ1, . . . , λn allocated to eachcard into electrical signals, discrimination is performed to determinewhether these electrical signals are distributed transmission signals orevaluation signals. When arriving signals are distributed transmissionsignals, each of the optical receiving cards 32-1, . . . , 32-n appliesthese distributed transmission signals to the delay compensation unit33. When arriving signals are evaluation signals, each of the opticalreceiving cards 32-1, . . . , 32-n obtains evaluation information andapplies this information to the receiving-side control signal processingunit 35. As evaluation information, for example, the bit error rate(BER) can be employed. This bit error rate indirectly reflects theoptical S/N ratio of the WDM transmission network. Instead of using thebit error rate as evaluation information, the evaluation signal may besubjected to waveform analysis in the state of optical signals, todirectly obtain the optical S/N ratio. Specifically, each of the opticalreceiving cards 32-1, . . . , 32-n constitutes an optical receivingunit.

Each of the optical receiving cards 32-1, . . . , 32-n may also applythe evaluation signals themselves to the receiving-side control signalprocessing unit 35, so that the receiving-side control signal processingunit 35 obtains evaluation information.

The delay compensation unit 33 compensates each of the input distributedtransmission signals (electrical signals) for transmission delay basedon differences in transmission routes in the WDM transmission network 1for each wavelength component λ1, . . . , λn, and applies the result tothe multiplexer 34. Information on the compensated transmission delaytime may be obtained from the receiving-side control signal processingunit 35, or may be received autonomously by the delay compensation unit33 according to header or other information.

The multiplexer 34 multiplexes the input plurality of distributedtransmission signals, and returns these signals to the transmissionsignal which was to be transmitted by the optical transmission device 3.Thereafter, this transmission signal is sent to a receiving terminal 5by means of an interface circuit with the receiving terminal 5 orsimilar, not shown. Specifically, the optical receiving cards 32-1, . .. , 32-n of FIG. 5, or, the receiving-side control signal processingunit 35, are constituent components of the transmission characteristicevaluation means.

The receiving-side control signal processing unit 35 is connected to thenetwork management device 6. This processing unit 35 provides evaluationinformation to the network management device 6, controls the quantity ofdelay information for each wavelength component λ1, . . . , λn in thedelay compensation unit 33 based on route setting information from thenetwork management device 6, controls the multiplexing method used bythe multiplexer 34 (to accommodate signal distribution on the side ofthe optical transmission device 3), and performs other operations. Ifthere are wavelength components not used in the current communication,operation of the corresponding optical receiving cards may beprohibited, so as to suppress unnecessary power dissipation.

The receiving-side control signal processing unit 35 also monitors theoccurrence of defects in each of the optical receiving cards 32-1, . . ., 32-n. If a defect occurs in any of the optical receiving cards, thenetwork management device 6 is notified of this fact.

(A-1-4) Network management device 6

FIG. 6 is a block diagram showing the functional configuration of thenetwork management device 6. The network management device 6 may, forexample, comprise information processing devices centered on a CPU whichexecutes software; but the configuration shown in FIG. 6 can also beemployed, to implement functions for rerouting based on initial use, anNE malfunction, or at other times. The functions of each part are alsoclear from an explanation of operation, and so are briefly explainedhere.

In FIG. 6, the network management device 6 has, as principal components,information storage means 40, optimal route selection means 41,transmission efficiency optimization means 42, route transmissionquality adjustment means 43, and communication means 44. The networkmanagement device 6, including, specifically, the principal components,operates as a wavelength component-specific route setting device.

The information storage means 40 has a transmission networkconfiguration storage unit 40 a, route usage status storage unit 40 b,transmission quality information storage unit 40 c, and defectinformation storage unit 40 d, and other components.

The transmission network configuration storage unit 40 a storesinformation on the configuration itself of the WDM transmission network1. The unit stores information on nodes comprised by the network(including information on exchange functions for each of the wavelengthcomponents λ1, . . . , λn), and information on optical fibers (physicalpaths) connecting nodes.

The route usage status storage unit 40 b stores information on routesfor each wavelength component λ1, . . . , λn currently in use and onempty band capacity and other information for the routes of eachwavelength component λ1, . . . , λn, associated with networkconfigurations of the WDM transmission network 1.

The transmission quality information storage unit 40 c stores evaluationinformation for the routes described above, and other information ontransmission quality.

The defect information storage unit 40 d stores defect information forrepeater nodes, optical fibers, and other network elements (NEs) in theWDM transmission network 1, as well as defect information for opticalchannel cards 13 in the optical transmission device 3 and opticalreceiving cards 32 (32-1 to 32-n) in the optical receiving device 4, andsimilar information.

The optimal route selection means 41 has an empty route search unit 41 aand empty route evaluation unit 41 b.

The empty route search unit 41 a searches for an empty route (inactuality, often a plurality exist) for each wavelength component λ1, .. . , λn, connecting the optical transmission device 3 and opticalreceiving device 4 which are the objects of routing. Here, theinformation stored by the transmission network configuration storageunit 40 a and route usage status storage unit 40 b, and otherinformation, is referenced. Routes containing as elements NEs for whichdefects are stored in the defect information storage unit 40 d areexcluded from the search.

For wavelength components for which not even one empty route is found,the empty route evaluation unit 41 b notifies the transmissionefficiency optimization means 42 that there are no optimal routes; forwavelength components for which a single empty route is found, the emptyroute evaluation unit 41 b notifies the transmission efficiencyoptimization means 42 that that empty route is the optimal route; andfor wavelength components for which two or more empty routes are found,the empty route evaluation unit 41 b evaluates those empty routes,determines an optimal route, and notifies the transmission efficiencyoptimization means 42.

As necessary, the empty route evaluation unit 41 b also evaluatesoptimal routes for each wavelength component.

In order to determine the optimal route from a plurality of emptyroutes, evaluation signals are transmitted via each of the empty routes,and the optimal route is determined as the route for which theevaluation values, propagation time, and other transmissioncharacteristics captured by the optical receiving device 4 are best.While differing from the explanation of operation given below, theoptimal route may also be determined based on evaluate values captured,propagation times, and other information from the past (as recent aspossible). When numerous empty routes have been found, the optimal routemay be determined based on evaluation values, propagation times, andother information after first reducing the number of candidates on thebasis of transmission distance, number of hops, or other criteria (thatis, the transmission distance, number of hops, and other acceptanceconditions may be imposed to reduce in advance the number of emptyroutes found). When there is a plurality of best empty routes, theoptimal route may be determined based on the transmission distance,number of hops, or other criteria.

The transmission efficiency optimization means 42 has aband-transmission efficiency evaluation unit 42 a, a signal distributiondetermination unit 42 b, and other components. The band-transmissionefficiency evaluation unit 42 a and signal distribution determinationunit 42 b coordinate to constantly revise the details of distribution oftransmission signals to each of the optical channel cards 13-1, . . . ,13-n. In this embodiment of the invention, as described in the sectionon operation, the transmission efficiency optimization means 42functions during transmission of transmission signals. Prior to thebeginning of transmission of transmission signals, the transmissionefficiency optimization means 42 may evaluate the used band capacity andtransmission efficiency, and determine the method of distribution of thetransmission signals. The transmission efficiency may, for example, be aparameter which is higher when used band capacities are balanced foreach route, and lower when used band capacities are in imbalance foreach route.

In this first embodiment, in essence the inverse-multiplex method isconsidered, so that when an optimal route is obtained for wavelengthcomponents for the necessary number of channels or greater (if p showsnumber of channels, then p≦n), the transmission efficiency optimizationmeans 42 makes a determination such that the transmission signal isdistributed to p optical channel cards. In this determination, it isdesirable, with respect to the transmission efficiency, that selectionbe performed from the wavelength components with greater empty bandcapacity, taking propagation delay into consideration.

The necessary number of channels p is, for example, the value obtainedby dividing the amount of data of the transmission signal by the amountof data which can be handled in one transmission operation by each ofthe optical channel cards 13-1, . . . , 13-n (the amount of data thatcan be accumulated in the buffer (not shown) within the optical channelcard).

The route transmission quality adjustment means 43 mainly monitors thetransmission quality (for example, the above-described evaluationinformation) for each route during transmission of transmission signals,and if the transmission quality drops, lengthens the clock signal periodof the optical channel cards 13-1, . . . , 13-n and otherwise tries tosecure the minimum level of transmission quality. This monitoring oftransmission quality is performed for, for example, wavelengthcomponents with little empty band capacity. Specifically, the routetransmission quality adjustment means 43 of FIG. 6 constitutes thetransmission quality management means.

The communication means 44 executes communication of control informationbetween the optical transmission device 3, optical receiving device 4,and other components.

(A-2) Operation of the First Embodiment

Next, each type of operation of the wavelength division multiplex systemof the first embodiment of this invention, having the configurationdescribed above, is explained.

(A-2-1) Basic transmission operation

When a transmission signal is input to the optical transmission device 3from a transmission terminal 2, the transmission signal is distributedamong each of the wavelength components λ1, . . . , λn according to thedistribution details (distribution method) set by the signal distributor12. The distributed transmission signals (electrical signals) areconverted into optical signals at prescribed respective wavelengths λ1,. . . , λn in each of the optical channel cards 13-1, . . . , 13-n, andthereafter are wavelength-multiplexed in the wavelength divisionmultiplexer 15, and the WDM signal is sent to the WDM transmissionnetwork 1.

In the WDM transmission network 1, the WDM signal output from theoptical transmission device 3 arrives at the opposing optical receivingdevice 4, via the routes set for each of the wavelength components λ1, .. . , λn.

In the optical receiving device 4, an arriving WDM signal isdemultiplexed into optical signals with the wavelength components λ1, .. . , λn, respectively, by the wavelength division demultiplexer 30, andthe optical signals of the wavelength components λ1, . . . , λn areapplied to the corresponding optical receiving cards 32-1, . . . , 32-n,respectively. Each of the optical receiving cards 32-1, 32-n convertsthe optical signal for each of the wavelength component λ1, . . . , λnallocated to it into an electrical signal. After conversion, the delaycompensation unit 33 compensates the electrical signals corresponding toeach of the wavelength components for propagation delays due todifferences in the routes of each of the wavelength components λ1, . . ., λn; the result is then multiplexed by an electrical multiplexer 34,and the transmission signal to be transmitted by the opticaltransmission device 3 is regenerated and sent to a receiving terminal 5.

(A-2-2) Initial route selection operation

Next, the flow chart of FIG. 7 is used to explain initial routeselection operation, executed prior to the start of communication oftransmission signals by the optical transmission device 3 and opticalreceiving device 4, to determine which routes to select.

If the optical receiving device 4 which communicates with the opticaltransmission device 3 is fixed, and there are no changes between eachcommunication, then upon introduction into the system of the opticaltransmission device 3 and optical receiving device 4, the processing ofFIG. 7 is executed.

Suppose that a transmission signal is applied from the transmissionterminal 2, so that the need to start new communication arises. In thiscase, the signal distributor 12 in the optical transmission device 3divides the transmission signal into unit data amounts which can behandled by each optical channel card 13-1, . . . , 13-n in a singletransmission operation (limited data amounts at transmission ratescorresponding to the existing connected WDM transmission network 1), andaccumulates the result internally, and at the same time notifies thenetwork management device 6 of the need to start new communication (stepS1).

At this time, the network management device 6 searches for empty routesfor each wavelength component λ1, . . . , λn connecting the opticaltransmission device 3 and optical receiving device 4 which are tocommunicate, and notifies the optical transmission device 3 of thisempty route information (step S2).

The control signal processing unit 17 of the optical transmission device3 receiving this notification applies the empty route information foreach of the wavelength components λ1. . . , λn to the correspondingoptical channel cards 13-1, . . . , 13-n. Each optical channel card13-1, . . . , 13-n labels the empty routes (one route, or a plurality ofroutes) such that evaluation signals (optical signals) having thatwavelength component are transmitted over these routes, and then each ofthe optical channel cards 13-1, . . . , 13-n transmits evaluationsignals to the WDM transmission network (step S3).

In the optical receiving device 4 upon receiving evaluation signals fromthe WDM transmission network 1 via empty routes, each of the opticalreceiving cards 32-1, . . . , 32-n determines the optimal route fromamong the single empty route or plurality of empty routes for thatwavelength component, based on the evaluation signals for its ownwavelength component; the network management device 6 is then notifiedof these optimal routes and transmission quality information (theevaluation information described above in this first embodiment), viathe receiving-side control signal processing unit 35 (step S4). Thenetwork management device 6 can also be made to determine the optimalroute from among one empty route or a plurality of empty routes for thesame wavelength component.

The network management device 6 compares transmission qualityinformation for the optimal routes for each wavelength component; basedon the comparison results, determines (that is, specifies) thewavelength components (optimal routes) in the required number for use intransmission; and notifies the optical channel cards for the pluralityof wavelength components thus determined of the optimal routes, while atthe same time sending notification to instruct switching from theevaluation signal transmission state to the transmission state fortransmission signals distributed on optimal routes (steps S5, S6).Instead of instructing direct switching to the transmission state fordistributed transmission signals, instructions can instead be issued toswitch to a state in which distributed transmission signals can be sent,with transmission of distributed transmission signals performed afterthe distribution method has been determined. At the time of selectionand determination of optimal routes, the band capacity at the time theamount of signal distribution is added to the candidate empty routes isconsidered. For example, if q wavelength components are set to the sameempty route, then if the band capacity for this empty route is exceeded,it is made the optimal route for (q−1) or fewer wavelength components.

Optical channel cards which have completed switching from the evaluationsignal transmission state to the state for transmission of distributedtransmission signals to optimal routes notify the network managementdevice 6 of this fact (step S7), and the network management device 6waits for notification of the completion of switching from all opticalchannel cards (step S8).

Having received notification of completion of switching from all opticalchannel cards, the network management device 6 or similar begins thesignal distribution processing shown in FIG. 8.

When the initial route selection operation described above is completed,transmission signals are, for example, distributed equally among aplurality of wavelength components (optical channel cards) used intransmission.

(A-2-3) Signal distribution operation

Next, the signal distribution operation (signal distribution adjustmentoperation) is explained, referring to the flow chart of FIG. 8. Signaldistribution operation is executed not only during the start ofcommunication described above, on completion of initial route selectionoperations in which wavelength components to be used and their optimalroutes have been determined, but also upon completion of review ofroutes at the time of occurrence of NE defects, described below. Inaddition, this signal distribution operation is also executedperiodically.

The network management device 6 evaluates the used band capacity (inother words, the empty band capacity) and transmission efficiency forall wavelength components (routes) transmitting distributed transmissionsignals (step S10).

Here, information for all NEs (network elements) existing on a route ismanaged by the network management device 6, so that by evaluating thecurrent state of traffic for each route and comparing the evaluationsobtained with evaluations of band capacity allocated to that route,knowledge of empty band capacity can be obtained.

The network management device 6 constantly evaluates empty band capacityfor all wavelength components during transmission, and in addition sendsinformation to the signal distributor 12 so as to enable optimization ofused band capacity and transmission efficiency, to cause revision of thedistribution of signals to all wavelength components at whichtransmission is in progress (step S11). For example, in the case ofroutes (transmission paths) the transmission bands of which haveequivalent capacities, signals are distributed to each wavelengthcomponent such that the same information quantities are sent via eachroute, taking the information transmission efficiency of the networkinto account.

Thereafter, the network management device 6 marks wavelength componentsfor which there is sufficient empty band capacity (at or above athreshold value) after review of distribution, and maintains the emptyband state for these wavelength components (step S12). Such wavelengthcomponents are utilized as wavelength components for switching in theevent of occurrence of a defect in an optical channel card, describedbelow.

After distribution review, the network management device 6 also sets, asobjects for transmission quality management, those wavelength componentsfor which there is no empty band capacity, or for which the empty bandcapacity is below the threshold value (step S13).

Wavelength components which have been set as objects for transmissionquality management are subjected to transmission quality evaluation atprescribed intervals and also to transmission speed control, as shown inFIG. 9, explained below.

(A-2-4) Operation for evaluation and control of transmission quality

Next, operation is explained, referring to the flow chart of FIG. 9, inwhich transmission quality is evaluated for wavelength components whichhave been set as the objects for management of transmission quality, andcontrol is performed accordingly.

When setting a prescribed wavelength component as an object fortransmission quality management, step S13 in the above-described FIG. 8is used.

At each prescribed period, or when processing by step S23 is completedin operations on the occurrence of a defect in an optical channel card,described below, the network management device 6 begins the processingof FIG. 9. Then, for wavelength components which are the objects oftransmission quality management, the management device 6 readstransmission quality information from the optical receiving cards of theoptical receiving device 4 (step S15), and makes a pass/fail judgment onthe state of the transmission quality (step S16).

For example, a CRC or other error detection code could be inserted intothe distributed transmission signal for transmission (with processingperformed by the signal distributor 12 or another component), and basedon this, the bit error rate (BER) could be obtained as transmissionquality information. Or, an evaluation signal could be added before orafter the distributed transmission signal and transmission performed,and the BER could be obtained as transmission quality information basedon the result of receiving the evaluation signal. By means of an aspectsuch as the modification of the first embodiment, described below,transmission quality information can be obtained directly by opticalmeans.

If, for a wavelength component which is an object of transmissionquality management, there is leeway in the transmission quality, thenetwork management device 6 instructs the optical channel card of theoptical transmission device 3 for the wavelength component to raise theclock frequency. On the other hand, if the transmission quality of thewavelength component is degenerated, the management device 6 instructsthe optical channel card of the optical transmission device 3 for thewavelength component to lower the clock frequency. If the transmissionquality is at the standard level, the management device 6 instructs theoptical channel card of the optical transmission device 3 for thewavelength component to maintain the clock frequency (step S17). Inother words, by executing reviews of the transmission speed (clockfrequency) in accordance with the transmission quality, the opticalchannel card is controlled so as to achieve its optimal transmissionspeed.

(A-2-5) Operation on the occurrence of defects in optical channel cardsand optical receiving cards

Next, the operation (rerouting operation) to review the distribution ofdistributed transmission signals when a defect occurs in any of theoptical channel cards of the optical transmission device 3, used intransmission of distributed transmission signals, is explained,referring to the flow chart of FIG. 10. Specifically, constituentmembers which are the object of malfunction detection, such as forexample optical channel cards 13, are called as internal constituentmembers.

Even when a defect occurs in any of the optical receiving cards of theoptical receiving device 4, the operation shown in this FIG. 10 isexecuted.

When the network management device 6 either is notified by the opticaltransmission device 3 of the occurrence of a defect in any of theoptical channel cards, or recognizes the occurrence of a defect in anyof the optical channel cards of the optical transmission device 3, afterfirst finding empty band capacity in the wavelength components providedfor transmission of distributed transmission signals based oninformation stored by the management device itself (see step S12 in FIG.8), a judgment is performed as to whether there are wavelengthcomponents with empty band capacity (steps S20, S21).

Then, if there is even one wavelength component having empty bandcapacity, the network management device 6 instructs the signaldistributor 12 to distribute the transmission signal capacity (datacapacity) which had been distributed to the optical channel card inwhich the defect occurred to all the wavelength components having emptyband capacity, and by this means the method of distribution oftransmission signals in the signal distributor 12 is modified (stepS22).

After the conclusion of the processing shown in FIG. 10, when theabove-described processing of FIG. 8 is begun, the presence or absenceof empty band capacity is confirmed for wavelength components for whichband capacity (data capacity) have been added, and as a result,wavelength components are set as objects for transmission qualitymanagement as necessary. When a wavelength component is set as an objectfor transmission quality management, the above-described processingshown in FIG. 9 is executed.

On the other hand, when there exist no wavelength components havingempty band capacity, the network management device 6 instructs thesignal distributor 12 to distribute transmission signal capacity (datacapacity) which had been distributed to an optical channel card(wavelength component) in which a defect has occurred to all wavelengthcomponents currently used in transmission other than the wavelengthcomponent of the optical channel card in which the defect has occurred.By means of this instruction, the method of distribution of transmissionsignals in the signal distributor 12 is changed, and at the same timeclock frequencies are lowered to accompany the addition of data capacity(step S23). After this processing, instead of returning to the mainroutine, the above-described processing of FIG. 9 (processing to controltransmission speeds according to transmission quality) is immediatelyexecuted. As is easily understood from the above explanation, when adefect occurs in an optical channel card 13 or optical receiving card32, the network management device 6 performs a distribution reviewoperation (rerouting operation), and operates to avoid internal defects;hence this network management device 6 functions as an opticaltransmission unit internal defect avoidance means.

The reason for lowering clock frequencies as described above is toprevent in advance the possibility that adequate transmission qualitycannot be maintained owing to the addition of data quantities in a statein which there is no empty band capacity.

(A-2-6) Operation upon occurrence of defects in network elements (NEs)

Next, operation to review the distribution of distributed transmissionsignals (rerouting operation) on the occurrence of defects in networkelements (NEs) is explained, referring to the flow chart of FIG. 11.

When notified by the WDM transmission network 1 that a defect hasoccurred in one of the NEs, or upon recognizing that a defect hasoccurred in one of the NEs, the network management device 6 treats theNE in which the defect has occurred as an element provided on routes,and searches for empty routes for all wavelength components, notifyingthe optical transmission device 3 of the information on these emptyroutes (step S25).

On receiving this notification, the transmission-side control signalprocessing unit 17 of the optical transmission device 3 provides thecorresponding optical channel cards with the information on empty routesfor each of the respective wavelength components, and after labeling theempty routes (one route, or a plurality of routes) such that evaluationsignals (optical signals) having the wavelength components aretransmitted on the routes, each optical channel card transmits anevaluation signal to the WDM transmission network 1 (step S26).

In the optical receiving device 4, after being provided with evaluationsignals from the WDM transmission network 1 via empty routes, eachoptical receiving card determines the optimal route from among one or aplurality of empty routes for that wavelength component, based on theevaluation signal of the wavelength component for that card, andnotifies the network management device 6 of the optimal route andtransmission quality information via the receiving-side control signalprocessing unit 35 (step S27).

The network management device 6 compares transmission qualityinformation for the optimal routes for each wavelength component, andfor each wavelength component determines the optimal route to replacethe route which has until now been used, as well as notifying theoptical channel card for the wavelength component responsible for thenewly determined optimal route; at the same time, the management deviceissues an instruction to switch from the transmission state forevaluation signals to the transmission state for distributedtransmission signals on optimal routes (steps S28, S29).

Optical channel cards which have completed switching from thetransmission state for evaluation signals to the state enablingtransmission of distributed transmission signals to new optimal routesnotify the network management device 6 of this fact (step S30), and thenetwork management device 6 waits for notification of the completion ofswitching from all optical channel cards instructed to perform switching(step S31).

Having received notification of completion of switching from all opticalchannel cards, the network management device 6 or similar begins thesignal distribution routine shown in FIG. 8, described above.

When beginning the processing of FIG. 8 described above, the presence orabsence of empty band capacity is confirmed for wavelength components(including other wavelength components) switched to new optimal routesfrom optimal routes passing through NEs in which defects have occurred.Based on the results of this confirmation, switched wavelengthcomponents are, as necessary, set as wavelength components as an objectfor transmission quality management. If a wavelength component is set asan object for transmission quality management, the processing shown inFIG. 9 described above is executed, and the transmission speed iscontrolled appropriately.

(A-3) Advantageous Results of the First Embodiment

According to the wavelength division multiplex transmission system ofthe first embodiment of the present invention, optimal routes areselected for each wavelength component, in consideration of transmissioncharacteristics and other information, so that satisfactory transmissioncharacteristics can be achieved compared with conventionalconfigurations.

Further, according to the first embodiment, the band capacity used andtransmission efficiency for each wavelength component are judged, anddata quantities are distributed dynamically among wavelength components,so that transmission efficiency of routes in use is appropriatelydivided, and as a result the concentration of data in a given route canbe prevented.

According to the first embodiment, transmission quality is monitored forwavelength components with little or no empty band capacity, and clockfrequencies are changed according to the transmission quality, so that aminimum transmission quality can be maintained for such wavelengthcomponents as well.

According to the first embodiment, even when a defect occurs in anetwork element, the optimal routes are re-selected, taking opticaltransmission characteristics into account, for each wavelength componentof routes on which the element is provided as a route element, andredistribution of the data quantities for these wavelength components isperformed. Hence congestion can be prevented, and compared withconventional configurations, the probability of circuit breaks arisingin the event of occurrence of defects in network elements can belowered.

According to the first embodiment, upon occurrence of a defect in anoptical channel card or optical receiving card, data quantities forwavelength components related to the defect are simply redistributed toother wavelength components according to empty band capacity, so thatmeasures can be taken promptly. In such redistribution, the clockfrequency is changed appropriately for wavelength components the bandcapacity of which has become constricted, so that at least a certaindegree of transmission quality can be maintained.

(A-4) Modification of the First Embodiment

In the above explanation of the first embodiment, various modifiedembodiments were also mentioned; in addition, a modified embodiment suchas the example indicated below can be cited.

The method used to obtain information for evaluating routes or fordetermining transmission quality is not limited to that explained in theabove first embodiment.

For example, in order to determine transmission quality or evaluateroutes, if parameters such as optical power information in each of thewavelength components are necessary at the optical signal stage in theoptical transmission device 3, the optical transmission device 3 may beconfigured such that optical couplers 18-1, . . . , 18-n are provided tobranch the emitted light output from each of the optical channel cards13-1, . . . , 13-n, as shown in FIG. 12, and branched monitor light fromthese optical couplers is input to the transmission-side control signalprocessing unit 17. In this case, there must be a photoelectricconverter within the transmission-side control signal processing unit17.

Or, for example, in order to determine transmission quality and evaluateroutes, if output light power information and other parameters from theoptical transmission device 3 at the WDM signal stage is necessary, theoptical transmission device 3, as shown in FIG. 13, may be configuredsuch that optical couplers 18 are provided which branch output light onthe back-stage side of the wavelength division multiplexer 15, so thatbranched monitor light from the optical couplers is input to thetransmission-side control signal processing unit 17. In this case also,there must be a photoelectric converter within the transmission-sidecontrol signal processing unit 17.

Or, for example, in order to determine transmission quality and evaluateroutes, the optical transmission device 3 may be configured such that aninstruction signal or similar to cause the optical channel cards 13-1 to13-n to output evaluation signals (optical signals) is applied to theoptical channel cards 13-1 to 13-n from the transmission-side controlsignal processing unit 17 via the signal distributor 12, as shown inFIG. 14.

Of course the modified embodiments of the optical transmission device 3shown in FIG. 12 through FIG. 14 may be combined freely.

For example, in order to determine transmission quality and evaluateroutes, if parameters such as optical power information in each of thewavelength components of the received light in the optical receivingdevice 4 are necessary at the optical signal stage, the opticalreceiving device 4 may be configured such that optical couplers 37-1, .. . , 37-n are provided to branch light incident on each of the opticalreceiving cards 32-1, . . . , 32-n as shown in FIG. 15, and branchedmonitor light from these optical couplers is input to the receiving-sidecontrol signal processing unit 35. In this case, there must be aphotoelectric converter within the receiving-side control signalprocessing unit 35.

Or, for example, in order to determine transmission quality and evaluateroutes, if parameters at the WDM signal stage such as optical powerinformation for the light input to the optical receiving device 4 arenecessary, the optical receiving device 4 may be configured such that onthe front-stage side of the wavelength division demultiplexer 30 isprovided an optical coupler 37 to branch the output light, with branchedmonitor light from this optical coupler input to the receiving-sidecontrol signal processing unit 35, as shown in FIG. 16. In this casealso, there must be a photoelectric converter within the receiving-sidecontrol signal processing unit 35.

Or, for example, in order to determine transmission quality and evaluateroutes, the method by which the receiving-side control signal processingunit 35 captures evaluation and other information from the opticalreceiving cards 32-1 to 32-n may be a method which captures theinformation via the delay compensation unit 33, as shown in FIG. 17.

Of course the modified embodiments of the optical receiving device 4shown in FIG. 15 through FIG. 17 may be combined freely.

Because the transmission-side control signal processing unit 17 andreceiving-side control signal processing unit 35 function by means ofsignals, in some cases they may be omitted.

Evaluation signals are transmitted at times other than when settinginitial routes also. Such methods include, in addition to the method ofdividing the transmission time for distributed transmission signals andthe transmission time for evaluation signals, the method of intermixingdistributed transmission signals and evaluation signals; or, aftermodulation of distributed transmission signals and evaluation signalswhile varying the method of electrical modulation, they may besuperposed and converted into optical signals, and simultaneouslytransmitted.

(B) Second Embodiment

Next, a second embodiment of the wavelength division multiplextransmission system of this invention is explained in detail, referringto the drawings.

It is suitable that the configuration of this second embodiment be theconfiguration of the operating system and/or standby system in a systemadopting a redundant configuration, as in the fifth and sixth aspectsdescribed below.

(B-1) Configuration of the Second Embodiment

FIG. 18 is a block diagram showing the configuration of principalcomponents of the optical transmission device 3X of the secondembodiment; parts which are the same or corresponding in FIG. 3 for thefirst embodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the opticaltransmission device 3X of this second embodiment is provided with anauxiliary optical channel card 13-S. The auxiliary optical channel card13-S functions whenever a defect occurs in one of the optical channelcards 13-1 to 13-n or in one of the optical receiving cards 32-1 to 32-nof the opposing optical receiving device 4X (see FIG. 19). A wavelengthcomponent λ1, different from the wavelength components λ1 to λn of theoptical channel cards 13-1 to 13-n, is allocated to the auxiliaryoptical channel card 13-S; except for this fact, the internalconfiguration is the same as for optical channel cards 13-1 to 13-n.

FIG. 19 is a block diagram showing the configuration of principalcomponents of the optical receiving device 4X of the second embodiment;parts which are the same or corresponding in FIG. 5 for the firstembodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the opticalreceiving device 4X of this second embodiment is provided with anauxiliary optical receiving card 32-S. The auxiliary optical receivingcard 32-S functions when the auxiliary optical channel card 13-S of theoptical transmission device 3X is functioning. Of course the auxiliaryoptical receiving card 32-S performs receiving operations for theoptical signal of the wavelength component λs; except for this fact, itis similar to the optical receiving cards 32-1 to 32-n.

In the case of this second embodiment, the WDM transmission network 1 isconfigured so as to be able to accommodate optical signals with thewavelength component λs.

(B-2) Operation of the Second Embodiment

Next, each type of operation of the wavelength division multiplex systemof the second embodiment of the present invention is explained.Operations other than operations when a defect occurs in any of theoptical channel cards is similar to the operation of the firstembodiment, and so an explanation is omitted.

FIG. 20 is a flow chart showing the operations in the event ofoccurrence of a defect in any of the optical channel cards. Even when adefect occurs in any of the optical receiving cards, the operations ofFIG. 20 are executed.

When notified by the optical transmission device 3 that a defect hasoccurred in one of the optical channel cards, or upon recognizing that adefect has occurred in one of the optical channel cards of the opticaltransmission device 3, the network management device 6 sends the variousparameters for the optical channel card in which the defect has occurred(for example, route, power, transmission speed) to the auxiliary opticalchannel card 13-S, and by this means the optical channel card 13-S isset in a state enabling transmission according to the various parameters(step S35).

Next, upon recognizing that settings have been completed, the networkmanagement device 6 instructs the signal distributor 12 to send to theauxiliary optical channel card 13-S distributed transmission signalswhich had been distributed to the optical channel card in which thedefect occurred (step S36). By this means, the auxiliary optical channelcard 13-S performs transmission of distributed transmission signals inplace of the optical channel card in which the defect occurred (stepS37).

If a defect occurs in one of the optical channel cards or opticalreceiving cards in a state in which the auxiliary optical channel card13-S and auxiliary optical receiving card 32-S are already being used,operation similar to the operation in the first embodiment, shown inFIG. 10 above, is executed.

(B-3) Advantageous Results of the Second Embodiment

According to of the wavelength division multiplex transmission system ofthe second embodiment of this invention also, advantages similar tothose of the first embodiment can be obtained.

Further, according to the second embodiment, even if a defect occurs inone of the optical channel cards or optical receiving cards normallyused in transmission, by providing an auxiliary optical channel card13-S and auxiliary optical receiving card 32-S on the transmission sideand receiving side respectively, transmission (defect recovery) can beperformed without reducing the number of channels (number of wavelengthcomponents) of transmission signals. Hence a system can be realizedwhich is more robust with respect to congestion than the firstembodiment of the invention.

(B-4) Modification of the Second Embodiment

The system which was cited as a modification of the first embodimentalso represents a modification of the second embodiment.

In the above explanation, the case in which there is one auxiliarywavelength component (optical channel card and optical receiving card)was described; but a plurality can be prepared as well.

Further, in the above explanation the route of the auxiliary wavelengthcomponent was the same as the route of the optical channel card oroptical receiving card in which the defect has occurred; but the systemmay be configured such that a search for the optimal route is performedfor the auxiliary wavelength component as well. This search may beperformed after a defect has occurred in one of the optical channelcards or optical receiving cards. Or, the optimal route for theauxiliary wavelength component may be determined in advance at the timeof determination of optimal routes for all wavelength components.

In the above explanation, the auxiliary wavelength component was fixed;however, the system may be configured such that the auxiliary wavelengthcomponent can be selected so that, when determining optimal routes forall wavelength components, the auxiliary wavelength component is, forexample, the wavelength component for which the evaluation result waslowest.

(C) Third Embodiment

Next, a third embodiment of the wavelength division multiplextransmission system of this invention is explained in detail, referringto the drawings.

It is suitable that the configuration of this third embodiment be theconfiguration of the operating system and/or standby system in a systemadopting a redundant configuration, as in the fifth and sixth aspectsdescribed below.

(C-1) Configuration of the Third Embodiment

FIG. 21 is a block diagram showing the configuration of principalcomponents of the optical transmission device 3Y of the thirdembodiment; parts which are the same or corresponding in FIG. 3 for thefirst embodiment are assigned corresponding symbols.

In addition to the configuration of the first embodiment, the opticaltransmission device 3Y of this third embodiment is provided with anauxiliary optical channel card 13-t and optical switch (optical SW) 19.

The auxiliary optical channel card 13-t functions when a defect occursin one of the optical channel cards 13-1 to 13-n. This auxiliary opticalchannel card 13-t of the third embodiment can capture, underinstructions from outside, wavelengths within the range of thewavelength components λ1 to λn for all the optical channel cards 13-1 to13-n. That is, the auxiliary optical channel card 13-t is a variablewave length optical channel card.

FIG. 22 is a block diagram showing an example of the detailedconfiguration of the auxiliary optical channel card 13-t(variable-wavelength optical channel card) of the third embodiment;parts which are the same or corresponding in FIG. 4 for the firstembodiment are assigned corresponding symbols.

In the auxiliary optical channel card 13-t of FIG. 22, avariable-wavelength (tunable) LD light source 20Y can be employed as thelight source. The auxiliary channel card 13-t is configured such that,by applying a wavelength instruction to this variable-wavelength LDlight source 20Y from the transmission-side control signal processingunit 17, an optical signal having the desired wavelength can be sent.

The optical switch 19 (FIG. 21) selects n optical signals from among theoptical signals from the optical channel cards 13-1 to 13-n and theauxiliary optical channel card 13-t, for a total of n+1 optical channelcards, and outputs these signals to the wavelength division multiplexer15, according to exchange instructions from the transmission-sidecontrol signal processing unit 17.

For example, in a state in which no defects have occurred in the opticalchannel cards 13-1 to 13-n ordinarily used in transmission, the opticalswitch 19 selects the optical signals from the optical channel cards13-1 to 13-n as they are, and applies them to the wavelength divisionmultiplexer 15.

Or, for example, in a state in which a defect has occurred in theoptical channel card 13-1, the optical switch 19 selects the opticalsignals from the optical channel cards 13-2 to 13-n and from theauxiliary optical channel card 13-t, and applies them to the wavelengthdivision multiplexer 15.

In the case of this third embodiment, the configuration of the opticaltransmission device 3Y differs from that of the above-described firstembodiment, but the configuration of the optical receiving device 4 isthe same as that of the first embodiment.

(C-2) Operation of the Third Embodiment

Next, operation of the wavelength division multiplex transmission systemof the third embodiment is explained. Operations other than operationswhen a defect occurs in any of the optical channel cards is similar tothe operation of the first embodiment, and so an explanation is omitted.

FIG. 23 is a flow chart showing operation when a defect occurs in one ofthe optical channel cards.

On being notified by the optical transmission device 3 that a defect hasoccurred in one of the optical channel cards (hereafter assumed to becard 13-1), or on recognizing that a defect has occurred in one of theoptical channel cards (13-1) of the optical transmission device 3, thenetwork management device 6 sends to an auxiliary variable-wavelengthoptical channel card 13-t the various parameters (for example,wavelength, route, power, transmission speed) of the optical channelcard 13-1 in which the defect has occurred, and by this means theauxiliary variable-wavelength optical channel card 13-t is set to astate in which transmission can be performed according to the variousparameters (steps S40, S41).

Through these settings, the auxiliary variable-wavelength opticalchannel card 13-t is put into a state in which optical signals with thewavelength component λ1 of the optical channel card 13-1 in which adefect has occurred can be sent. In other words, the auxiliaryvariable-wavelength optical channel card 13-t becomes a pseudo-opticalchannel card 13-1.

The network management device 6 instructs the optical switch 19 toperform exchanges such that optical signals from the auxiliaryvariable-wavelength optical channel card 13-t are input to the inputpoint of the wavelength division multiplexer 15 at which optical signalsfrom the optical channel card 13-1 in which the defect has occurred hadbeen input; as a result, the optical switch 19 changes to an exchangestate conforming to this instruction (steps S42 and S43).

After confirming that the variable-wavelength optical channel card 13-tand optical switch 19 have executed the state changes and otherinstructions, the network management device 6 instructs the signaldistributor 12 to apply to the auxiliary variable-wavelength opticalchannel card 13-t the distributed transmission signals which had beendistributed to the optical channel card 13-t in which the defect hadoccurred (step S44).

By this means, the variable-wavelength optical channel card 13-t behavesas if it were the optical channel card 13-1 in which the defect hasoccurred.

If a defect occurs in one of the optical channel cards while in a statein which the auxiliary variable-wavelength optical channel card 13-t isalready in use, the operation of the above-described first embodiment isexecuted.

(C-3) Advantageous Results of the Third Embodiment

According to the wavelength division multiplex transmission system ofthe third embodiment of the present invention also, advantages similarto those of the first embodiment can be obtained. In addition, throughthe third embodiment, the following advantages can be gained.

Similarly to the second embodiment, the configuration of the thirdembodiment also has provided an auxiliary optical channel card 13-t; butbecause this auxiliary optical channel card 13-t can accommodatevariable wavelengths, it can, effectively, operate as an optical channelcard in which a defect has occurred, and as a result there is no need toprovide an auxiliary configuration in the optical receiving device 4,nor is it necessary that the WDM transmission network 1 accommodate anauxiliary wavelength component.

(C-4) Modification of the Third Embodiment

The system which was cited as a modification of the first embodimentalso represents a modification of the third embodiment.

In the above explanation, a configuration in which there is oneauxiliary variable-wavelength optical channel card in the opticaltransmission device was described; but a configuration in which aplurality of auxiliary variable-wavelength optical channel cards areprovided is also possible. When providing such a plurality of auxiliaryvariable-wavelength optical channel cards, these optical channel cardsmay be configured such that the variable wavelength ranges are differentfor each. For example, the first auxiliary variable-wavelength opticalchannel card may accommodate wavelengths from λ1 to λm, and the secondauxiliary variable-wavelength optical channel card may accommodatewavelengths from λ(m+1) to λn.

In the above, an auxiliary variable-wavelength optical channel cardconfigured so as to employ a light source which itself is of variablewavelength was described; but of course the configuration to achievevariable wavelength is not limited to this. For example, avariable-wavelength optical channel card may be realized by having lightsources for each wavelength component, and by selecting a signal fromthe plurality of light sources.

In the above, a configuration was described in which the opticaltransmission device is provided with an auxiliary variable-wavelengthoptical channel card and optical switch; but the optical receivingdevice may be provided with an optical switch and auxiliaryvariable-wavelength optical receiving card. That is, an optical signalwith the wavelength component of an optical receiving card in which adefect has occurred may be applied to an auxiliary variable-wavelengthoptical receiving card via an optical switch, and the auxiliaryvariable-wavelength optical receiving card may receive and process theoptical signal with that wavelength component.

(D) Fourth Embodiment

Next, a fourth embodiment of the wavelength division multiplextransmission system of the present invention is explained in detail,referring to the drawings.

It is suitable that the configuration of this fourth embodiment be theconfiguration of the operating system and/or standby system in a systemadopting a redundant configuration, as in the fifth and sixth aspectsdescribed below.

The configurations of the optical transmission device and opticalreceiving device in the wavelength division multiplex transmissionsystem of the fourth embodiment can be respectively represented by FIG.4 and FIG. 5 of the above-described first embodiment.

However, in this fourth embodiment, the detailed internal configurationof each of the optical channel cards 13-1 to 13-n in the opticaltransmission device 3 differs from that of the first embodiment.

FIG. 24 is a block diagram showing the detailed configuration of theoptical channel cards 13Z (13-1 to 13-n) of the fourth embodiment; partswhich are the same or corresponding in FIG. 4 for the first embodimentare assigned corresponding symbols.

In addition to the configuration of the optical channel card 13 of thefirst embodiment, the optical channel cards 13Z of the fourth embodimentare provided with an auxiliary LD light source 20Z and optical coupler26.

Upon the occurrence of a defect in the LD light source 20, the auxiliaryLD light source 20Z emits continuous-wave light at the same wavelengthas the LD light source 20, in place of the LD light source 20. Here, theauxiliary LD light source 20Z is configured so as to incorporatefunctions for detection of the occurrence of defects in the LD lightsource 20. For example, a configuration is assumed in which the interiorof the auxiliary LD light source 20Z comprises a photosensitive elementwhich monitors light emitted from the LD light source 20, so that whenthe optical power incident on the photosensitive element drops below athreshold value, it is assumed that a defect has occurred in the LDlight source 20, and emission operation of the auxiliary LD light source20Z is started.

The optical coupler 26 guides continuous-wave light emitted from the LDlight source 20, or continuous-wave light emitted from the auxiliary LDlight source 20Z, to the optical modulator 21.

Next, operation in the event that a defect occurs in the LD light source20 of an optical channel card 13Z is briefly explained.

When a defect occurs in the LD light source 20 of an optical channelcard 13Z, switching from the LD light source 20 to the auxiliary LDlight source 20Z occurs, by means of the defect evasion function withinthe optical channel card 13Z. Either the transmission-side controlsignal processing part 17 or the network management device 6 is notifiedof information during the period of this switching to the auxiliary LDlight source 20Z, and during this switching interval, the signaldistributor 12 is controlled to perform transmission without using theoptical channel card 13Z. For example, prior to defect occurrence,switching is performed from a state in which a distributed transmissionsignal with n wavelength components is being sent, to a state in which adistributed transmission signal with n 1 wavelength components is beingsent. Rather than redistribute data, for example, output from the signaldistributor 12 to the optical channel card 13Z is halted.

Then, after confirming that switching to the auxiliary LD light source20Z is completed, the system returns to the transmission state using theoptical channel card 13Z. That is, switching is performed from a statein which distributed transmission signals are sent using n−1 wavelengthcomponents, to a state in which distributed transmission signals aresent using n wavelength components.

According to the wavelength division multiplex transmission system ofthe fourth embodiment of this invention also, advantages similar tothose of the first embodiment can be obtained. In addition, through thefourth embodiment, the following advantages can be gained.

According to the fourth embodiment, simply by making a slight change tothe internal configuration of optical channel cards, defects in opticalchannel cards can easily be accommodated. In actuality, the LD lightsource 20 is a part in the optical channel card which frequentlymalfunctions; by providing an auxiliary system, a satisfactory effect asa defect-avoidance function is obtained.

Further, through simple control to stop the output of distributedtransmission signals from the signal distributor 12 during the intervalof switching from the LD light source 20 to the auxiliary LD lightsource 20Z, and to resume the output of distributed transmission signalsafter the completion of switching, defects in light sources can beavoided.

In the above, the provision of LD light sources with an auxiliary systemwas explained; auxiliary systems may also be provided for the entiretyof the optical processing system parts, including the LD light sourceand optical modulator.

(E) Fifth Embodiment

Next, a fifth embodiment of the wavelength division multiplextransmission system of the present invention is explained in detail,referring to the drawings.

(E-1) Configuration of the Fifth Embodiment

FIG. 25 is a block diagram showing the configuration of principalcomponents of the wavelength division multiplex transmission system ofthe fifth embodiment; parts which are the same or corresponding indrawings for previously-described embodiments are assigned correspondingsymbols.

In FIG. 25, in the wavelength division multiplex transmission system ofthe fifth embodiment also, the optical transmission device 3W andoptical receiving device 4W are linked to each other through a WDMtransmission network 1.

The optical transmission device 3W has an operating-system opticaltransmission unit 3WA, a standby-system optical transmission unit 3WS,and a system switch 7. Though omitted in FIG. 25, the opticaltransmission device 3W also has circuitry for interfaces withtransmission terminals (one terminal, or a plurality thereof) at eachlayer.

The system switch 7 essentially provides transmission signals to theoperating-system optical transmission unit 3WA. When a defect occurs inthe operating-system optical transmission unit 3WA sufficient tonecessitate exchange, transmission signals are applied to thestandby-system optical transmission unit 3WS, based on controlinformation from a defect detection configuration, not shown, within theoptical transmission device 3W, and the network management device, notshown, and similar.

The operating-system optical transmission unit 3WA has a signaldistributor (so-called IMP) 12A, optical channel cards 13-1A to 13-nA,wavelength division multiplexer 15A, control signal processing unit 17A,and other components. In the case of the fifth embodiment, theoperating-system optical transmission unit 3WA transmits such that allwavelength components pass through the same route, and in this respectthe configuration is the same as in the prior art.

A difference between the operating-system optical transmission unit 3WAand the prior art is that the control signal processing part 17Amonitors defects in the optical channel cards 13-1A to 13-nA, and, fordefects in up to a prescribed number (for example, one) of opticalchannel cards, the signal distributor 12A is instructed to distributethe transmission signals distributed [to cards in which] defects haveoccurred to other optical channel cards. Hence the signal distributor12A also differs from the prior art in that it supports such changes insignal distribution. Specifically, the control signal processing unit17A functions as part of the defect detection means. That is, thecontrol signal processing unit 17A monitors defects in the opticalchannel cards 13-1A, . . . , 13-nA, and makes judgments on the presenceof defects based on the results of detection by externally providedsensors and other detection means.

On the other hand, the standby-system optical transmission unit 3WSfunctions when there occur defects in a number of optical channel cardsin the operating-system optical transmission unit 3WA which exceeds theprescribed number.

The standby-system optical transmission unit 3WS has a signaldistributor 12S, optical channel cards 13-1S to 13-nS, wavelengthdivision multiplexer 15S, and other components. In the case of thisfifth embodiment, the standby-system optical transmission unit 3WS isconfigured so as to send and process all wavelength components so as topass through the same route, in a configuration similar to that ofconventional optical transmission devices.

The optical receiving device 4W has an operating-system opticalreceiving unit 4WA, standby-system optical receiving unit 4WS, andsystem switch 8. Though omitted in FIG. 25, the optical receiving device4W also has circuitry for interfaces with receiving terminals (notlimited to one terminal) at each layer.

The system switch 8 selects the transmission signal received from theoperating-system optical receiving unit 4WA and transmission signalreceived from the standby-system optical receiving unit 4WS, and sendsit to the receiving terminal side, not shown; that is, it functions toswitch between systems.

The operating-system optical receiving unit 4WA and standby-systemoptical receiving unit 4WS each have a wavelength division demultiplexer30A, 30S, receiving cards 32-1A to 32-nA and 32-1S to 32-nS, and othercomponents; it performs reception processing similar to that ofconventional optical receiving devices. In the device shown in FIG. 25,the multiplexer unit 34 at the electrical signal stage is common to bothsystems. Of course, both systems may comprise separate multiplexer unitsas well.

(E-2) Operation of the Fifth Embodiment

In the wavelength division multiplex transmission system of the fifthembodiment, when a defect occurs in any of the optical channel cards ofthe operating-system optical transmission unit 3WA while in thetransmission state using the operating-system optical transmission unit3WA, the control signal processing unit 17A instructs the signaldistributor 12A to distribute transmission signals to the other n−1optical channel cards, and switching to a state of transmission of WDMtransmission signals using n−1 wavelength components is performed.

Such processing is nearly the same as the processing shown in the flowchart of FIG. 10 for the first embodiment.

This measure, in which the number of distributed transmission signals ischanged, is employed when the number of optical channel cards in whichdefects have occurred is equal to or less than a prescribed number (forexample, one).

When the number of defects in the optical channel cards 13-1A to 13-nAin the operating-system optical transmission unit 3WA exceeds theprescribed number, the system switch 7 causes transmission signals to beapplied to the standby-system optical transmission unit 3WS, andswitching to a state in which transmission is by the standby-systemoptical transmission unit 3WS is performed.

When the operating-system optical transmission unit 3WA is restored tothe normal state through replacement of units and parts or similar, thesystem returns to the state of transmission by the operating-systemoptical transmission unit 3WA.

(E-3) Advantageous Results of the Fifth Embodiment

According to the wavelength division multiplex transmission system ofthe fifth embodiment of the present invention, even when a defect occursin an optical channel card or cards in the operating-system opticaltransmission unit 3WA, if the number of defects is equal to or less thana prescribed number, the defects can be avoided without switchingsystems.

From the absence of a need for system switching, there is the subsidiaryadvantage that, for example, line breaks and other risks uponmalfunction of the system switch can be avoided. Further, restoration tonormal is possible through the replacement of the optical channel cardsin which defects have occurred, so that only a small quantity ofoperating system optical transmission units, which are large-size parts,must be stocked in consideration of the occurrence of defects.

In the case of adoption of a simple redundant configuration, if a defectoccurs in an operating-system optical channel card, switching to thestandby system is immediately performed; but if a defect has alsooccurred in a standby-system optical channel card (if duplicate defectsoccur), transmission is no longer possible. However, in the case of thisfifth embodiment, even if a defect occurs in optical channel cards ofthe operating-system optical transmission unit 3WA, if the number iswithin the prescribed number, transmission by the operating system canbe continued. In the case of this fifth embodiment, switching to thestandby system is performed when a greater number of defects occurs, sothat the configuration of this embodiment has a higher degree ofredundancy, and satisfactory functions for defect avoidance.

(E-4) Modification of the Fifth Embodiment

In the above explanation, a system was described in which theoperating-system optical transmission unit alone can executetransmission operation with a small number of wavelength components(number of channels); as shown in FIG. 26, a control signal processingunit 17S may be provided in the auxiliary-system optical transmissionunit, enabling internal accommodation even when there are defects in aprescribed number or fewer of the optical channel cards 13-lS to 13-nS.Upon doing so, the degree of redundancy is further increased.

In the above explanation, a system was described with a configuration inwhich, at the time of occurrence of a defect in an internal opticalchannel card, the operating-system optical transmission unit canaccommodate without executing system switching; conversely, thestandby-system optical transmission unit alone may comprise such aconfiguration.

Further, in the above explanation a system was described in which allwavelength components pass through the same route between the opticaltransmission device and optical receiving device; but the technicalconcept in which routes are determined for each wavelength component, asin the above-described first through fourth embodiments, may also beintroduced. In particular, it is desirable that the optical transmissiondevice and optical receiving device of the above-described first throughfourth embodiments be applied as the operating-system opticaltransmission unit and the operating-system optical receiving unit. By sodoing, considerable transmission quality can be attained even if defectsoccur in some of the optical channel cards.

(F) Sixth Embodiment

Next, a sixth embodiment of the wavelength division multiplextransmission system of the present invention is explained in detail,referring to the drawings.

(F-1) Configuration of the Sixth Embodiment

FIG. 27 is a block diagram showing the configuration of principalcomponents of the wavelength division multiplex transmission system ofthe sixth embodiment; parts which are the same or corresponding in FIG.25 for the fifth embodiment are assigned corresponding symbols.

Compared with the wavelength division multiplex transmission system ofthe above-described fifth embodiment, the wavelength division multiplextransmission system of the sixth embodiment differs in the configurationof the operating-system optical transmission unit 3WA. The defect alarmpopulation message communication unit 50 of FIG. 27 constitutes thedefect alarm message generation means.

In the case of the sixth embodiment, the operating-system opticaltransmission unit 3WA has, in addition to the configuration of the fifthembodiment, a defect alarm population message communication unit 50.

When a defect occurs in any of the optical channel cards 13-1A to 13-nAin the operating-system optical transmission unit 3WA, the defect alarmpopulation message communication unit 50 sends, to the maintenancemember management terminal 51, via a prescribed communication network 52(which may be leased lines), a defect alarm population messagecontaining specific information on the optical transmission device 3Wand its optical channel cards.

Here, the defect alarm population message communication unit 50 may berealized as one function of the signal distributor 12A and controlsignal processing unit 17A.

The communication network 52 used for transmission of defect alarmpopulation messages may be the WDM transmission network 1, or may be acommunication network different from the WDM transmission network 1.

When the communication network 52 used for transmission of defect alarmpopulation messages is the WDM transmission network 1, a dedicatedwavelength component used for transmission of defect alarm populationmessages is established, and optical signals with this wavelengthcomponent are used to transmit defect alarm population messages. In thiscase, the defect alarm population message communication unit 50comprises an optical channel card.

The maintenance member management terminal 51 is provided in, forexample, a warehouse which stocks maintenance members, or a so-calledvendor company or similar which has delivered the optical transmissiondevice 3W. That is, the maintenance member management terminal 51 isprovided in a company, division, or similar which is responsible forreplacement of optical channel cards or other members in which defectsoccur.

The maintenance member management terminal 51 comprises an informationprocessing device having functions to receive the above-described defectalarm population messages. When the maintenance member managementterminal 51 receives a defect alarm population message, it performs theprescribed replacement processing (an example of replacement processingis explained in the section on operation).

(F-2) Operation of the Sixth Embodiment

In this sixth embodiment also, when a defect occurs in any of theoptical channel cards 13-1A to 13-nA in the operating-system opticaltransmission unit 3WA, transmission signals are redistributed to theother optical channel cards excluding the optical channel card in whichthe defect has occurred, and are sent to the optical receiving device4W.

By means of this operation, the defect alarm population messagecommunication unit 50 sends to the maintenance member managementterminal 51, via the communication network 52, a defect alarm populationmessage containing specific information on the optical transmissiondevice 3W and the optical channel card in which the defect has occurred.

At this time, the maintenance member management terminal 51 may performprocessing sufficient to sound an alarm and display the defect alarmpopulation message; or, it may confirm inventory of the optical channelcard of the defect alarm population message, if there is a card instock, set a reservation for its use, and if there is no card in stock,issue an instruction to manufacture or to order a card from anotherwarehouse. Further, a maintenance worker may reference schedules orother data and establish a date and time for replacement operation.

Further, the maintenance member management terminal 51 may transfer thedefect alarm population message to another device as necessary.

(F-3) Advantageous Results of the Sixth Embodiment

According to the sixth embodiment also, advantages similar to those ofthe fifth embodiment are obtained. In addition the following advantagescan be obtained.

According to the sixth embodiment, the system is configured such that,upon occurrence of a defect in an optical channel card, the defect alarmpopulation message communication unit 50 sends a defect alarm populationmessage too the maintenance member management terminal 51, so thatreplacement of the optical channel card can be performed promptly.Further, to the extent that the defect alarm population message is sentin realtime, inventory management and manufacturing management areexpedited, and smaller stock quantities can be anticipated.

(F-4) Modification of the Sixth Embodiment

In the above, a system was described in which a defect alarm populationmessage communication unit 50 is provided in the operating-systemoptical transmission unit 3WA; a configuration may also be adopted inwhich, in addition to this, or in place of this, a defect alarmpopulation message communication unit is provided in the standby-systemoptical transmission unit 3WS. A configuration may also be adopted inwhich a defect alarm population message communication unit is providedin the operating-system optical receiving unit 4WA and standby-systemoptical receiving unit 4WS. Further, a configuration may be adopted inwhich, in a system which does not adopt the redundant configuration ofan operating system and standby system as in the first through fourthembodiments, a defect alarm population message communication unit isprovided in the optical transmission device and optical receivingdevice. Of course, the member executing communication of defect alarmpopulation messages is not limited to optical channel cards.

In the above, a system was described in which the defect alarmpopulation message communication unit 50 transmits directly a defectalarm population message to the maintenance member management terminal51; but transmission of the message may also be via the networkmanagement device. In this case, the transmission-side control signalprocessing unit comprises the defect alarm population messagecommunication unit 50.

Further, a defect alarm population message communication unit may beprovided in the transmission device and receiving device of atransmission system other than a wavelength division multiplextransmission system.

(G) Other Embodiments

In the above explanations of each embodiment of the present invention, aconception was explained in which there is one transmission terminal andone receiving terminal connected to the optical transmission device andthe optical receiving device respectively; but a plurality oftransmission terminals and receiving terminals may be connected as well.In this case, functions for switching of transmission signals betweentransmission terminals, and functions for switching receivedtransmission signals between receiving terminals, may be performed by asignal distributor 12 incorporating buffer memory and a multiplexer 34.

If the combination is possible, a wavelength division multiplextransmission system may be constructed by combining the opticaltransmission device of one embodiment with the optical receiving deviceof a different embodiment.

In the above, the case of one-to-one communication between an opticaltransmission device and an optical receiving device was described; butthe technical concepts of this invention can also be applied to one-to-Ncommunication.

In the above, it was shown that communication from an opticaltransmission device to an arbitrary optical receiving device ispossible; the technical concepts of the presenst invention can also beapplied to cases in which the optical receiving device which engages incommunication with the optical transmission device is fixed. In thiscase, when the optical transmission device and optical receiving deviceare inserted into a system, searches for optimal routes for eachwavelength component and other processing may be performed.

The configuration of the WDM transmission network is arbitrary, and maybe a star shape, loop shape, mesh shape, or multiple networks of aplurality of loops. Further, the optical transmission devices andoptical receiving devices of each of the above embodiments may beprovided at intermediate nodes. For example, the technical concepts ofthis invention can be applied even when Add/Drop circuits and opticalcross-connect (OXC) devices exist at intermediate nodes.

As explained above, with a construction of a wavelength divisionmultiplex transmission system according to the invention, an opticaltransmission device comprises an operating-system optical transmissionunit and a standby-system optical transmission unit; transmissionsignals to be transmitted are distributed among a plurality ofwavelength components, converted into WDM signals, and sent to the WDMtransmission network; an optical receiving device comprises anoperating-system optical receiving unit and a standby-system opticalreceiving unit; and WDM signals from the WDM transmission network arerestored to the above transmission signals. In this wavelength divisionmultiplex transmission system, the above operating-system opticaltransmission unit and/or the above standby-system optical transmissionunit have optical transmission unit internal defect avoidance meanswhich, upon the occurrence of a prescribed number or fewer of wavelengthcomponent transmission defects, avoids defects within the opticaltransmission unit, so that the equivalent redundant configuration isexpanded, and defect avoidance functions can be enhanced.

With a construction of a communication device according to theinvention, there are provided defect detection means which detectsdefects in internal constituent members and defect occurrence membertransmission means. The defect occurrence member transmission means,when the above defect detection means detects a defect, sends defectoccurrence member information to an external maintenance membermanagement terminal which performs management of maintenance members,supply processing, or similar. Accordingly, shortening of the time fromdefect occurrence to restoration of the normal state can be expected,and in this respect defect avoidance functions can be enhanced.

1. A wavelength division multiplex transmission system which distributestransmission signals to be transmitted among a plurality of wavelengthcomponents, converts said signals into WDM signals, and transmits saidWDM signals to a WDM transmission network, and which restores WDMsignals from said WDM transmission network into said transmissionsignals; comprising an optical transmission device and optical receivingdevice, in which said optical transmission device comprises at least aplurality of operating-system optical transmission units associated withone standby-system optical transmission unit, and said optical receivingdevice comprises at least a plurality of operating-system opticalreceiving units associated with one standby-system optical receivingunit; wherein either said operating-system optical transmission units,or said standby-system optical transmission unit, or both, have opticaltransmission unit internal defect avoidance means which, upon theoccurrence of a prescribed number or fewer of wavelength componenttransmission defects, executes avoidance of defects within said opticaltransmission unit; wherein said operation-system optical transmissionunit and said standby-system optical transmission unit are configured totransfer said transmission signals at fixed respective wavelengths, suchthat said standby-system optical transmission unit is configured totransmit transmission signals using a transmission wavelength componentdifferent from that of the operating-system transmission unitsassociated with a wavelength component transmission defect; and whereinsaid standby-system optical receiving unit is configured to receive areceive wavelength component different from that of the operating-systemreceive units associated with a wavelength component receive defect. 2.A wavelength division multiplex transmission system according to claim1, in which said optical transmission unit internal defect avoidancemeans distributes the transmission signals which had been distributed tothe wavelength component related to a defect to another, normalwavelength component, and causes said signals to be transmitted, and inwhich said optical receiving device comprises defect detection means. 3.A communication device having defect detection means for detectingdefects in internal constituent members, having defect occurrence membertransmission means which, when said defect detection means detects adefect, sends defect occurrence member information to an externalmaintenance member management terminal which performs management ofmaintenance members, supply processing, or similar; an opticaltransmission device and optical receiving device, in which said opticaltransmission device comprises at least a plurality of operating-systemoptical transmission units associated with one standby-system opticaltransmission unit, and said optical receiving device comprises at leasta plural of operating-system optical receiving units associated with onestandby-system optical receiving unit; wherein said operating-systemoptical transmission units and said standby-system optical transmissionunit are configured to transfer transmission signals at fixed respectivewavelengths, such that said standby-system optical transmission unit isconfigured to transmit transmission signals using a transmissionwavelength component different from that of the operating-systemtransmission units associated with a wavelength component transmissiondefect; and wherein said standby-system optical receiving unit isconfigured to receive a receive wavelength component different from thatof the operating-system receive units associated with a wavelengthcomponent receive defect.
 4. A communication device according to claim3, in which said defect occurrence member transmission means sends saiddefect occurrence member information to the transmission network used bythe communication device for normal communication.